Don’t Even Think About Swapping Your LS Intake Until You Read This

Is an intake manifold an important part of a performance LS build? The answer is, obviously, yes. One need only look at the peak power difference between the least and most powerful intakes in this shootout was more than 60 hp. Imagine that, an intake swap that yielded 60 extra horsepower, but that isn’t the whole story. While peak power gains offer enticing Internet banter, changes in the entire power curve are the real story. That is why we are also including average power production from 3,000 to 7,000 rpm, torque production at 4,000 rpm, cost, throttle opening, runner length, composition, and even What We Liked and might change on each design. In short, this was the most extensive LS intake manifold test ever devised.

Though we know you have already skipped ahead to the data, there are two important points to consider. The first is that no intake test, including this LS extravaganza, is absolute. Intake manifolds are combination specific, meaning that the ideal intake for an 8,000-rpm stroker combination would be different than one designed for a stock 4.8L truck motor. If you’re looking for the “best” single intake on the market for every application—such an animal does not exist. This test should provide you info on what design might work best for your combo.

The Test Engine Speaking of combos, our test motor was built to simulate your basic hot street-strip setup. The iron-block 6.0L featured a stock block and crank mixed with Carillo rods and CP flat-top pistons. The Comp 469 cam offered a 0.617/0.624-inch lift split, a 231/247-degree duration split and 113-degree LSA. Topping the 6.0L was a set of AFR LSX 230 V2 heads. The various intakes were run with no less than eight different fuel rails, seven different throttle-bodies, and three different style injectors. Naturally, air/fuel, timing, and temperatures remained constant during testing. Check out the results to see how your favorite or future favorite fared.

What We Like: OEM quality and fitmentWhat We Don’t: Least powerful of all the factory intakes

Our testing began with the LS intake that started it all, the LS1. Least powerful of all the factory offerings, the LS1 definitely limited the power output of our 6.0L test motor. Equipped with the factory LS1 intake and Accufab 78mm throttle-body, the 6.0L produced peak numbers of 535 hp and 468 lb-ft of torque. This curve was to serve as the baseline for the remainder of the LS intakes.

What We Like: Factory fitment and better power than LS1What We Don’t: Limited availability and elevated price

First up was the LS6 intake. Designed as a factory upgrade for the LS1, the LS6 intake once again proved its reputation by significantly improving the power of our 6.0L. Compared to the LS1, the LS6 offered an additional 22 hp and 15 lb-ft of torque. The LS6 is harder to find and slightly more expensive than the LS1, but the power gains are worth it.

Naturally, we tested the factory truck intake, as GM made literally millions of trucks equipped with either the 4.8L, 5.3L, or 6.0L—all sharing the same intake. The popularity and price of 4.8L and 5.3L swaps means there are plenty of truck intakes to be had. Though the most affordable of all the factory offerings, the truck intake easily outperformed the LS1 by 14 hp and excelled at torque production, nearly matching the performance-oriented LS6. The average horsepower and torque production for the truck intake bested the LS1 and matched the high-powered LS6, making the truck intake a good choice for many applications.

What We Like: Bigger throttle opening and best overall factory performerWhat We Don’t: Limited availability and even more expensive than the LS6

Pendleton Serape Hoodie Popover Hoodie Stripe Stripe Serape Stripe Pendleton Hoodie Popover Serape Pendleton Popover Pendleton Serape Stripe Apparently, the GM engineers sharpened their power pencils when designing the intake for the Trail Blazer SS (TBSS), as this was not only the most powerful factory intake but outperformed the LS1 from top to bottom. Unlike the LS6 that matched the power of the LS1 down low (then took off), the TBSS intake offered more power and torque everywhere. By making more torque than the truck intake and more power than the LS6, the TBSS offered the best of both worlds.

What We Like: Low costWhat We Don’t: Like to see larger throttle opening and longer runners

Stepping into aftermarket cast-aluminum intake offerings, the Speedmaster intake offered shorter (and larger) runners than the LS1 as well as a larger throttle opening. The power gains were most consistent at the top of the rev range, but like the factory truck manifold, the Speedmaster even offered additional torque down low. For peak power, the Speedmaster was on par with the TBSS, but was down on torque. Something we really liked about the Speedmaster unit was, at $220, it could be purchased for little more than the factory TBSS intake. The cost and power made it a desirable alternative to the factory LS1 intake.

What We Like: Ease of installationWhat We Don’t: Small throttle opening and weight of cast-aluminum manifolds vs. composite

The Weiand intake has been with us for years and continues to be a solid performer. The Weiand handily outperformed not only the LS1 but all of the factory manifolds, including the Trail Blazer SS. Like the Speedmaster, the torque was down compared to the Trail Blazer SS manifold, but we soon discovered that only two other intakes would best the peak torque offered by the impressive Trail Blazer SS. An extra 31 hp more than the LS1 is a hefty chunk of power and shows just how limiting the factory manifold can be on a modified 6.0L.

What We Like: PerformanceWhat We Don’t: Weight and flexible bottom cover

The BBK was the final cast-aluminum, long-runner intake we tested, and it performed very well. With peak numbers of 568 hp and 489 lb-ft of torque, the SSI intake offered a solid combination. The BBK intake also looked the part, though a splash of black would really wake it up visually. Compared to the LS1, the SSI intake offered slightly more torque down low and shined as revs increased.

What We Like: Versatility and better hood clearance than Hi RamWhat We Don’t: Less power than Hi Ram

Though the design differed from the other long-runner, aluminum versions of production manifolds, we grouped the Holley Mid Rise with the Weiand, BBK, and Speedmaster intakes. The Mid Rise offered improved hood clearance compared to the Hi Ram, but the power gains were nowhere near as significant. Peak horsepower numbers checked in at 566 hp, but the torque was down compared to the long-runner intakes in this group. Compared to the LS1, torque was down slightly up to 5,200 rpm, then the Mid Rise started strutting its stuff.

What We Like: The originator with plenty of performanceWhat We Don’t: Small throttle opening and now takes a backseat to the LSXR versions

We had this original FAST/Wilson LSX intake laying around the shop, so we included it in the test. This intake started the composite revolution, and we’d like to know how many were sold to LS enthusiasts before they upgraded to the LSXR versions. This intake has never failed to impress with power gains over the LS1 (and LS6). Despite sharing the same throttle opening, this early FAST offered an additional 36 hp more than the LS1 and 14 hp more than the LS6.

Things got serious when we installed the 102mm FAST LSXR (it also offers a 92mm version that would be about 10 to 12hp down). Equipped with the LSXR, the modified 6.0L produced 591 hp and 505 lb-ft of torque. The FAST intake offered impressive peak power and the highest torque production of any of the intakes tested. Though some of the shorter runner intakes made slightly more peak power, it is hard to beat this long-runner design for average power production.

What We Like: Design improves entry into cylinder heads to increase powerWhat We Don’t: Height of intake may limit fitment

Theoretically, the straight runners in the 102mm LSXRT should improve power production, but the RT version managed to squeak past the (low profile) LSXR by just 1 hp. The two traded torque production, with the LSXR coming out on top 505 lb-ft to 502 lb-ft for the RT. Still, the LSXRT offered an impressive 57 hp and 34 lb-ft of torque more than the LS1.

What We Like: Another powerful composite LS manifold to choose fromWhat We Don’t: Slightly heavier than factory composites

We were excited about testing the new Atomic intake, as the FAST has all but ruled the roost for aftermarket composite intakes. The new Airforce intake demonstrated that the MSD designers brought their A game. Equipped with the new Atomic, the 6.0L pumped out 592 hp and 493 lb-ft of torque. With these results, obviously, the Atomic must be viewed as a serious player. Now we need to see how much boost it will take.

What We Like: Impressive visual statement and top-end powerWhat We Don’t: Fuel rails that use pipe fittings

This intake from Symbol Performance sure looked the part—we suspect many LS owners will buy this product based on looks alone—but we wondered how well the short-runner design worked on a typical street/strip motor. Like the single-plane, carbureted intakes we tested, this piece offered short intake runners designed to promote power production higher in the rev range, and that is exactly what it did. The short runner lost out in torque production to the LS1 at less than 5,300 rpm, then pulled away strongly thereafter, peaking at 587 hp (a gain of 52 hp).

What We Like: Looks/performs great and casting ensures no boost/vacuum leaks What We Don’t: Doesn’t use LS throttle-body pattern

The Edelbrock Pro-Flow shared the tunnel-ram design with the TSP and Holley Hi-Ram, but the runners were slightly longer than the TSP. The Edelbrock showed the effectiveness of this design by offering 593 hp (a gain of 58 hp) and 474 lb-ft of torque (up 6 lb-ft). Like the TSP, the Edelbrock was down compared to the LS1 below 4,700 rpm, but pulled away handily thereafter.

What We Like: Versatility and tunnel-ram design makes top-end powerWhat We Don’t: Like to see the attachment bolts for the lids come in from the top

The Hi-Ram was the horsepower king in this test, though by a scant 4 hp more than the Edelbrock Proflow (597 versus 593 hp). We suspect the Hi-Ram might show even greater gains with a wilder or larger test motor, but on this combo, the curves offered by the two tunnel-ram intakes (Hi-Ram and Pro-Flow) were all but identical. Like the others, the short-runner Hi-Ram traded torque below 4,700 rpm to the LS1, but motored away on the big end.

What We Like: Dual quads sticking through a hole in the hood attract attentionWhat We Don’t: Sometimes unwanted attention

Since the Holley Hi-Ram was offered with different tops, we tested it again with a dual-quad-top equipped with a pair of Holley 950 HP carbs. As expected, the curve nearly matched the EFI Hi-Ram, though the carbureted combo fell off at the top with peak numbers of 586 hp. Torque was up by 1 lb-ft with a peak of 475 lb-ft. The carbureted Hi-Ram showed once again that short runners excel at power production higher in the rev range than the factory LS1.

We also ran the Holley Mid-Rise in carbureted trim, though the dual-carb Mid-Rise was a more significant change in the intake design than the simple lid swap on the Hi-Ram. The Mid Rise required an intermediate section between the dual-quad lower and lid, which extended the runners slightly on the EFI version. The dual-quad-carbureted intake was run with a pair of 4160 carbs that lacked secondary metering blocks for jetting. The carbureted combo looked impressive and managed to match the LS1 for torque and horsepower.

The dual-plane Performer RPM showed its torquey nature by bettering the long-runner LS1 at less than 4,600 rpm. The dual-plane also offered more power at speeds of more than 6,300 rpm, but the LS1 was slightly better between those two extremes. This intake combo showed there was plenty of power for swap candidates who elect to run their LS with carburetion.

What We Like: Simplicity of carburetionWhat We Don’t: Loss of torque inherent in single-plane design

As expected, the single-plane Victor Jr. offered more peak power than the LS1, but the downside was that (unlike the dual-plane) power production suffered below 5,500 rpm. Like the tunnel-ram intakes, the single-plane design featured short runners, but where the tunnel-ram intakes offered the same runner length for all eight cylinders (for even power production), the single-plane featured four long(er) and four short(er) runners. This optimized power production from one set of four cylinders at a different rpm than the other.

What We Like: Offered good torque for a single planeWhat We Don’t: Still typical trade-off in low speed for top-end power

Though similar in design to the Victor Jr., the Holley single-plane intake offered slightly better torque than the Edelbrock, but slightly less peak power. The question now is would you trade the extra 24 lb-ft down low for a loss of 3 hp at the top?